More from WebMD

May 5, 2010 -- Two or three tablespoons a day of olive oil may help protect against ulcerative colitis, preliminary research suggests.

In a new study, people with the highest consumption of oleic acid -- a monounsaturated omega-9 fatty acid found in olive oil, peanut oil, and grapeseed oil, as well as in butter and certain margarines -- had an almost a 90% reduced risk of the inflammatory bowel disease, compared with those with the lowest intake.

"About half of the cases of ulcerative colitis could have been prevented if people consumed larger amounts of oleic acid -- 2 or 3 tablespoons of olive oil or the equivalent," says Andrew Hart, MD, of the University of East Anglia in Norwich, England.

Still, the findings need to be replicated before any definitive conclusions can be made, he tells WebMD.

Even if they do pan out, "we have to make sure that a diet high in oleic acid is not just linked to some other factor that is protective against ulcerative colitis," Hart says.

The findings were presented at Digestive Disease Week 2010 in New Orleans.

During bouts of ulcerative colitis, the large intestines become inflamed, causing diarrhea and discomfort.

"Oleic acids may dampen down inflammation in the bowel ... by blocking chemicals that stimulate inflammation," Hart says.

The new study involved 25,639 people ages 40 to 74 participating in the EPIC-Norfolk (European Prospective Investigation into Cancer) trial.

Tracking Diet in a Food Diary

When participants entered the study between 1993 and 1997, they completed a detailed seven-day food diary in which they were asked to record everything they ate and how much they ate of each item. Pictures helped them gauge portion size, and specially trained nutritionists helped interpret the findings, Hart says.

Then, software containing information on the nutrient content of more than 9,000 food items was used to calculate each person's intake of oleic acid and other fatty acids.

Over an average period of about four years, 22 people developed ulcerative colitis. For each person with colitis, four people of the same age and sex without the disorder were chosen for comparison.

These 110 participants were then divided into three groups based on their consumption of oleic acid.

Those in the highest third were 89% less likely to have ulcerative colitis than those in the lowest third.

The findings took into account other factors that can affect the development of ulcerative colitis, including cigarette smoking and intake of omega-3 and omega-6 polyunsaturated acids, which Hart says also influence the inflammatory process.

"A big strength" of the study was the accuracy of the computer program used to calculate dietary intakes of oleic acid, he says. One of the weaknesses was that participants only kept food diaries for one week.

If the findings do hold up in further research, oleic acid might be tested not only for the prevention of ulcerative colitis, but also as a treatment for people who already have the disorder, Hart says.

Kelly A. Tappenden, PhD, RD, of the University of Illinois in Urbana-Champaign, tells WebMD that while the results are "promising," further research is needed before any recommendations regarding oleic acid and ulcerative colitis can be made.

That said, olive oil "is an excellent choice" for meeting dietary recommendations for fat in your diet, she says.

American Heart Association guidelines call for getting no more than 30% of calories each day from fat, but studies show most Americans get far more.